The objective of this program is to conduct a comprehensive study of the molecular biology of prothrombin synthesis and the role of vitamin K and the coumarin anticoagulant drugs on its regulation. The discovery of a new amino acid gamma-carboxyglutamate in bovine prothrombin by Stenflo and his associates (P.N.A.S. 71, 2730, 1974) has helped to focus studies of vitamin K action on phenomena related to carboxylation of the precursor peptide. Several lines of study are in progress. These include the isolation and characterization of paraprothrombins from rat and chick, study of the action of vitamin K in the carboxylation of preprothrombin including requirements for in vitro formation of prothrombin in liver microsomes, identification of the CO(2) donor and mechanism of transcarboxylation, correlation of this phenomena with vitamin K binding and transplantation of the mRNA for prothrombin in a heterologous system in order to learn the true nature of preprothrombin. In addition, studies are in progress to isolate and characterize warfarin binding and vitamin K binding proteins from Sprague-Dawley and warfarin resistant rats. Work is also being continued on the purification of alkylating enzyme from menadione in chick liver microsomes. The ultimate goal of this program will be to reconstitute the vitamin K dependent system for prothrombin synthesis from purified constituents in artificial phospholipid membranes. BIBLIOGRAPHIC REFERENCES: Olson, R.E.: Vitamin K Deficiency. In CURRENT THERAPY, W.B. Saunders Company, p. 418, 1975; Olson, R.E.: Mode of Action of Vitamin K in Regulating Prothrombin Synthesis. In PROCEEDINGS OF THE IX INTERNATIONAL CONGRESS OF NUTRITION, S. Karger, Basle, Vol. 1, 70, 1975.